EFFECTS OF OXYGEN SUPER-SATURATED NUTRIENT SOLUTIONS ON GREENHOUSE TOMATO

Abstract

The effects of varying levels of nutrient solution oxygenation on greenhouse tomato (Lycopersicon esculentum L. 'Macarena') was investigated in 2006 and 2007 using rockwool, coir and perlite growing media. In 2006, early marketable and total yields were higher with 75 ppm O2 in the nutrient solution (14.5 kg m-2), than the control (12.8 kg m-2) and compressed air (12.9 kg m-2) treatments, while no significant difference was observed between 20, 30, 35 and 75 ppm. The seasonal yield followed the same trend, i.e. higher values were obtained with 75 ppm O2 (28.9 kg m-2) than with the control (27.1 kg m-2) and compressed air treatments (26.2 kg m-2). The seasonal average weight of marketable fruit was significantly higher with 35 ppm O2 (206 g) than with the control (196 g) and compressed air treatments (194 g). In 2007, in general, the late-season and seasonal marketable yield with all oxygen treatments was either equal to or higher than the control. Except for the 30 ppm treatment, the usual decline in marketable yield across the season was slower with oxygen super-saturated nutrient solution (24-29% between the mid and the last season) than with the control (i.e. a corresponding 40-45% reduction), indicating that oxygen can sustain productivity under ageing stress condition. The 60 ppm O2 treatment resulted in higher total seasonal yield than the control on the rockwool medium. These results suggest that application of nutrient solution oxygenation under certain conditions can improve greenhouse tomato productivity. Differences in climatic conditions may explain partly the differences in crop performance between the two seasons.